This invention relates to an image recording method and to an image recording apparatus.
Heretofore, in order to record an image on the basis of image data, a silver halide photographic material is exposed to a laser beam. Further, in recent years, it has appeared a thermally developable silver halide photosensitive material which is capable of visualizing an image by thermal development without using a liquid process. However, it has been proved that, if it is exposed to a laser beam, interference fringes are generated to produce unevenness of image. This phenomenon will be explained with reference to FIG. 15 which is a conceptional drawing showing the relation between the cross-section of a film and a laser beam.
As shown in FIG. 15(a), when a laser beam enters the film F, which is composed of a photosensitive layer of a thermally developable silver halide photosensitive material and a supporting member made of a PET film or the like, from its obverse surface F1, owing to a part of the beam being reflected by the reverse surface F2 and returns to the obverse surface F1, interference occurs between the beam B1 which directly enters the photosensitive layer and the beam B2 which is transmitted through the photosensitive layer, reflected by the surface F2 and further reflected by the obverse surface F1. For this reason, the light quantity which is applied to the photosensitive layer varies depending on the thickness of the film, and as a result of it, the amount of exposure for the thermally developable silver halide photosensitive material varies, to produce unevenness of density.
If the optical path difference xcex4 between the beam directly entering the photosensitive layer and the beam passing through the photosensitive layer after being reflected by the surfaces F2 and F1 is an integral multiple of the wavelength of the laser beam, the light quantity applied to the photosensitive layer becomes maximum, and if it is shifted by a half of the wavelength, the light quantity becomes minimum. The reflectance R at the boundary surface between two media having different refractive indices is expressed by the following equation (1):
xe2x80x83R=((nBxe2x88x92nA)/(nB+nA))2xe2x80x83xe2x80x83(1),
where nA and nB denote the refractive indices of the media being present at the both sides of this boundary surface respectively.
Now, for example, assuming that the refractive indices of the respective layers of the photosensitive material are the same and uniform, and that nA=1 (air) and nB=1.5 (photosensitive material), the reflectance R at the boundary surface between air and the photosensitive layer is 4%. Further, the variation of light quantity (peak to peak) xcex94A owing to interference can be expressed by the following equation (2), reaching a large value of 16%:
xcex94A=4Rxe2x80x83xe2x80x83(2).
Actually, as shown in FIG. 15(b), the variation of light quantity owing to interference becomes less than the above-described value, because a laser beam absorption layer is provided at the rear side of the reverse surface F2 and scattered light s is generated by the silver halide particles included in the photosensitive layer. However, if there is a slight difference of refractive index between the absorption layer and the photosensitive layer, reflection occurs at the boundary surface F2 of the absorption layer and the supporting member, to make the absorption layer not to contribute to the reduction of interference. Further, because the conventional photosensitive materials have large sized silver halide particles included, and are capable of being provided with multiple absorption layers, interference fringes are difficult to be generated in them, while a thermally developable photosensitive material has finer silver halide particles than the conventional photosensitive materials, and the light scattering in the photosensitive layer is much less than the conventional films, hence, interference becomes remarkable especially in the case of a high-contrast thermally developable photosensitive material having a xcex3 value (film contrast) of 2 or more.
It is possible to prevent the variation of light quantity owing to interference as described in the above by the countermeasures (a) to (c) as follows:
(a) By providing a reflection reducing film on the reverse surface of the supporting member (F2), the reflectance by the boundary surface F2 between the supporting member and the absorption layer is reduced.
(b) The dispersion of the thickness of the supporting member is suppressed to a fraction one over several or less of the wavelength of the laser beam (generally 0.5 to 1.5 xcexcm).
(c) By making smaller the difference of refractive index between the supporting member and the absorption layer, the reflectance R at the boundary surface F2 between the supporting member and the absorption layer is made smaller.
However, the countermeasure (a) results in the raise of cost, and is not favorable. Further, concerning the countermeasure (b), it is possible to suppress the dispersion of the medium having a thickness of several xcexcm, but it is nearly impossible to suppress the dispersion of the medium having a thickness of 100 xcexcm or more to a value under 1 xcexcm or smaller. Furthermore, regarding the countermeasure (c) too, because even a difference of refractive index of only 0.05 or smaller makes interference fringes, it is nearly impossible to adjust the difference of the refractive index between the both members to a value under this level.
Further, in the description of the U.S. Pat. No. 4,711,838, it is disclosed a thermally developable silver halide photosensitive material comprising a surface layer diffusing and transmitting the near infrared light which is in the wavelength region of a laser beam, a reverse surface layer diffuse-reflecting or absorbing this near infrared light, and a layer which is provided between the supporting member and the photosensitive layer and diffuse-transmits or absorbs this near infrared light. Heretofore, it is general to suppress interference fringes by devising the photosensitive material itself as described in the above. Further, in the publication of the TOKUHYOHEI 10-500229, it is disclosed that a laser diode is driven by an input signal for the laser diode to which a high-frequency signal is superposed.
However suppression of interference fringes by devising the photosensitive material gives a bad influence to other characteristics of the photosensitive material, for example, visibility after development and cost of the photosensitive material, or it is not sufficient by itself alone as the countermeasure. Further, the superposing of a high-frequency signal to the input signal for the laser diode is technically difficult, makes cost high, and possibly makes the operation all the more unstable, and further, it has the defect that it makes the efficiency of utilizing light about a half. Furthermore, in a high-contrast photosensitive material having a xcex3 value of 2 or larger, the suppression of interference fringes has not been made enough.
This invention has been made in view of the above-described problems in the conventional technology; it is an object of this invention to provide an image recording method and an image recording apparatus capable of improving the quality of an image which is formed on a photosensitive material, by reducing the interference fringes of the laser beam by a method which is different from conventional ones.
In order to accomplish the above-described subjects, the image recording method of this invention is an image recording method in which an image is formed on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average particle size of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, wherein said photosensitive material is subjected to exposure with an incident angle of the laser beam to said photosensitive material switched over from xcex81 to xcex82 at every predetermined number of scan lines in order that some integer N may satisfy the following expression:
(N+0.5xe2x88x92(0.7/xcex3)) less than (2nh/xcex)(cos xcex81xe2x80x2xe2x88x92cos xcex82xe2x80x2) less than (N+0.5+(0.7/xcex3))xe2x80x83xe2x80x83(3),
where N denotes an integer, n denotes the refractive index of the photosensitive material, h denotes the thickness of the photosensitive material, xcex denotes the wavelength of the laser beam, xcex81xe2x80x2 denotes the incident angle in the photosensitive layer of the laser beam which is incident at the incident angle xcex81, and xcex82xe2x80x2 denotes the incident angle in the photosensitive layer of the laser beam which is incident at the incident angle xcex82.
According to this invention, even for a high-contrast thermally developable silver halide photosensitive material having a xcex3 value of 2 or larger, interference fringes can be effectively reduced. Besides, for more effective reduction of interference fringes, it is desirable that an integer N satisfies the following expression (4):
(N+0.5xe2x88x92(0.4/xcex3)) less than (2nh/xcex)(cos xcex81xe2x80x2xe2x88x92cos xcex82xe2x80x2) less than (N+0.5+(0.4/xcex3))xe2x80x83xe2x80x83(4).
Further, the image recording method according to another embodiment of this invention is an image recording method in which an image is formed on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, wherein the incident angle of said laser beam to a pixel of said photosensitive material is different from that to a pixel adjacent to said pixel.
Further, the image recording method according to further embodiment of this invention is an image recording method in which an image is formed on a thermally developable silver halide photosensitive material by making a scanning exposure to a plurality of laser beams which scan substantially different scan lines from one another on said photosensitive material which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, wherein each of at least two laser beams of said plurality of laser beams has an incident angle to a pixel of said photosensitive material which is different from that to a pixel adjacent to said pixel.
Further, the method of image recording according to another embodiment of this invention is an image recording method in which an image is formed on a thermally developable silver halide photosensitive material by making a scanning exposure to a plurality of laser beams which scan the substantially same scan line on said photosensitive material which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, wherein at least two laser beams of said plurality of laser beams have respectively different incident angles to the same pixel of said photosensitive material.
Further, the image recording method according to a further another embodiment of this invention is an image recording method in which an image is formed on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, wherein a laser beam is split into a plurality of beams, said photosensitive material is subjected to a scanning exposure to the plural laser beams obtained by splitting, and at least two laser beams of said plural laser beams obtained by splitting scan substantially the same scan line for exposure and have respectively different incident angles to the same pixel of said photosensitive material.
Further, the image recording method according to a further another embodiment of this invention is an image recording method in which an image is formed on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, wherein the laser beam is split into a plurality of beams, said photosensitive material is subjected to a scanning exposure to the plural laser beams obtained by splitting, and each of at least two laser beams of said plural laser beams obtained by splitting has an incident angle to a pixel of said photosensitive material which is different from that to a pixel adjacent to said pixel.
According to each of the above-described image recording methods, even for a high-contrast thermally developable silver halide photosensitive material having a xcex3 value of 2 or more, interference fringes can be effectively reduced.
Further, it is desirable that the aforesaid photosensitive material includes a silver salt of an organic acid of an amount of 4 times in terms of silver quantity to the silver halide particles in the aforesaid photosensitive layer. If a silver salt of an organic acid of an amount of 4 times in terms of silver quantity to the silver halide particles in the photosensitive layer is included, the photosensitive material has a high visibility after development, to have the contrast easily made high, but interference fringes can be effectively reduced.
The source of the aforesaid laser beam can be made a laser diode.
Further, the image recording apparatus of this invention is an image recording apparatus forming an image on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, comprising a laser light source for emitting a laser beam, and an incident angle changing means for switching over the incident angle of said laser beam to said photosensitive material at every predetermined number of scan lines.
According to this invention, interference fringes can be reduced even for a high-contrast thermally developable silver halide photosensitive material having a xcex3 value of 2 or more. In this case, the above-described incident angle changing means is equipped with a light modulating element for varying the emerging angle of said laser beam, and by controlling the driving of this light modulating element, the incident angle can be switched over.
Further, the image recording apparatus of another embodiment of this invention is an image recording apparatus forming an image on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or more, comprising a laser light source for emitting a laser beam, a light splitting means for splitting said laser beam into a plurality of laser beams, and an optical system having such a structure as to make different the incident angles of said plurality of laser beams to said photosensitive material from one another.
Further, the image recording apparatus of further another embodiment of this invention is an image recording apparatus forming an image on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, comprising a plurality of laser light sources for emitting a laser beam, and an optical system having such a structure as to make different the incident angles of a plurality of laser beams to said photosensitive material from one another.
Further, the image recording apparatus of another embodiment of this invention is an image recording apparatus forming an image on a thermally developable silver halide photosensitive material by making a scanning exposure to a plurality of laser beams which scan substantially different scan lines from one another on said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, comprising a plurality of laser light sources for emitting a laser beam, a light splitting means for splitting said laser beam into a plurality of laser beams, and an optical system having such a structure as to make different the incident angles of at least two laser beams of said plurality of laser beams to said photosensitive material from one another.
Further, the image recording apparatus of further another embodiment of this invention is an image recording apparatus forming an image on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average diameter of 0.1 xcexcm or smaller provided on a supporting member having a thickness of 200 xcexcm or smaller, has the transmittance for the laser beam which is 20% or larger at the mean wavelength of the laser beam, and has a xcex3 value of 2 or larger, comprising a laser light source for emitting a laser beam, and a light splitting means for splitting said laser beam into a plurality of laser beams, wherein at least two laser beams of said plurality of laser beams scan substantially the same scan line for exposure and have different incident angles to said photosensitive material respectively.
According to each of the above-described image recording apparatus, interference fringes can be reduced even for a high-contrast thermally developable silver halide photosensitive material having a xcex3 value of 2 or larger.
Further, it is desirable that the aforesaid photosensitive material includes a silver salt of an organic acid of an amount of 4 times of the silver halide particles in the aforesaid photosensitive layer in terms of silver quantity. If a silver salt of an organic acid of an amount of 4 times in terms of silver quantity to the silver halide particles in the photosensitive layer is included, the photosensitive material has a high visibility after development, to have the contrast easily made high, but interference fringes can be effectively reduced.
Further, the source of the aforesaid laser beam can be made a laser diode. Besides, with respect to the switching over of the incident angle or making the incident angles different from one another, it is desirable to do it for incident angles against the sub-scanning direction.